The present invention relates to an arrangement for producing drawn formations on plate-shaped or sheet-shaped workpieces in general, and more particularly to an arrangement of this type for use in a pressing and cutting machine, especially such having a numerically controlled coordinate table, a vertically movable upper tool having a die, and a lower tool carrying an associated punch.
In the treatment of plate-shaped or sheet-shaped workpieces or, generally speaking, in the sheet metal working field, it is often necessary to produce drawn formations. Such drawn formations include, without limitation thereto, thread formations, air-passage slots or baffles, hollow formations or depressions, and deep-draw formations. In the entire sheet metal working industry, such drawn formations are customarily produced in conventional eccenter presses, so long as no special requirements exist and so long as individual operations are involved. Under such circumstances, the drawing die is provided on the pressing table and the punch is arranged on the upper tool under the ram. This means that the drawn formation, namely the respective depression, is formed in the respective workpiece in the downward direction. This is satisfactory in many applications.
However, when the drawn formations are to be formed on a cutting and pressing machine cooperating with a numerically controlled coordinate table, this working procedure is no longer acceptable, inasmuch as the just produced drawn formation would be destroyed or damaged during the transportation of the workpiece into the next-following position. In order to avoid such destruction or damage, it was necessary to reverse the working procedure, that is, to mount the punch on the lower tool and to provide the drawing die on the upper tool. The present invention is based on a drawing arrangement of this type.
Experience with this type of drawing arrangement has shown that the workpiece remains stuck on the punch which, in this case, constitutes a drawing mandrel, after the termination of the drawing operation, so that it has to be removed from the punch by a special stripping tool. In the known drawing arrangements of this type, the punch is rigidly connected with the lower tool, in such a manner that at least its most prominent portion extends above the surrounding area of the lower tool, that is, the support surface for the workpiece, at least to a distance corresponding to the drawing depth, in order to assure an unproblematical stripping. However, such a construction is possessed of grave disadvantages. On the one hand, the free space between the drawing die and the stripping tool as it is customarily provided is narrowed thereby, with the consequence that, ultimately, even the drawing depth is limited. On the other hand, the tool plane of the cutting and pressing machine, that is, the plane determined by the support surfaces for the workpieces, does not remain level with the often used tool magazine; rather, an elevated portion, or a plurality of elevated portions, extends upwardly of the aforementioned plane, and the workpiece must be transported over such elevated portion or portions. This has further the consequence that, when a tool magazine, such as an indexing turret carrying the tools, is being used, the operating stations which are arranged adjacently to the drawing station equipped with the rigid punch or mandrel can no longer be used for normal cutting operations.